WO2022046241A1

WO2022046241A1 - Supported ocm catalyst composition having reduced new phase content

Info

Publication number: WO2022046241A1
Application number: PCT/US2021/036358
Authority: WO
Inventors: Wugeng Liang; Yu-Lun Fang; Azim ALI; Hector PEREZ; Pankaj Singh Gautam; David West
Original assignee: Sabic Global Technologies, B.V.
Priority date: 2020-08-28
Filing date: 2021-06-08
Publication date: 2022-03-03

Abstract

The invention relates to a catalyst composition comprising (a) an oxide phase (A) comprising one or more metal oxide or metal hydroxide components, each of which is represented by the general formula (I) (AE_aRE1_bRE2_cAT_d(OH)_kO_x), (b) a supported oxide phase (B) comprising one or more metal-support oxide components, each of which is represented by the general formula (II) (AE_aRE1_bRE2_cAT_dM_zO_p), and (c) a metal oxide support represented by the general formula (M_mOn)_t (SiO₂)_1-t, wherein further the weight ratio 'R' of supported oxide phase (B) to total weight of oxide phase (A) and supported oxide phase B (i.e B/A+B) is less than equal to (<=) 0.5, and the variables defining the general formula (I) and (II) are as defined herein in this disclosure. The invention further provides one or more methods for preparing such a catalyst composition. Additionally, the invention also describes a process for producing C₂₊ hydrocarbons, using such a catalyst composition.

Description

SUPPORTED OCM CATALYST COMPOSITION HAVING REDUCED NEW PHASE CONTENT

FIELD OF INVENTION

[0001] The invention relates to the field of catalyst compositions used for the oxidative coupling of methane (OCM).

BACKGROUND

[0002] Methane is a widely available feedstock and if oxidatively coupled, in presence of certain methane coupling catalysts, commercially high value chemicals, such as ethylene and other C2+ hydrocarbons, can potentially be produced at high production margins. However, one of the reasons why catalyst systems for the oxidative coupling of methane has not been used commercially, is because traditional OCM catalyst system suffer from low catalytic activity as well as low product selectivity. Product selectivity, in particular is a concern for OCM processes where the severe reaction conditions often lead to the production of thermodynamically stable carbon oxide products (CO_X) instead of the commercially desired C2+ hydrocarbons. In addition, the existing catalyst systems have poor mechanical integrity, which are not suitable for commercial applications especially under severities of an OCM reaction process.

[0003] One possible way of achieving the desired level of catalyst performance in terms of selectivity is by using a metal oxide support in OCM catalyst systems. For commercial application of these catalysts, it is believed that catalyst support provides required strength and thereby improves catalyst performance. However, supported catalyst systems often contain oxide species (“new phase”), which is formed by the partial reaction between the metal oxide support and the active catalyst system. For example, it was observed that when the catalyst active component is supported on alumina (AI2O3), there may be a reaction occurring between the active components of the catalyst and alumina, resulting in the formation of “new phases”. For illustration, a multicomponent OCM catalyst, such as a system represented by the empirical formula SrLaNdYbOx, when supported on an alumina, may result in the formation of new phase oxide species such as aluminates (SrAhOzi, LaAlOs, SrLaAlO4) as shown below:

SrO + AI2O3 SrAl₂O₄

La2O3 + AI2O3 — LaAKL

SrO + La2O3 + AI2O3 —> SrLaAlO4 [0004] Although the new phase oxide species can catalyze OCM reactions by themselves, they however tend to lower the C2+ hydrocarbon selectivity performance of the OCM catalyst and impeding the overall performance of active catalyst components, such as SrO, and LazOg. Therefore, there is a need to control the formation of these new phase oxide species for preventing the deterioration in catalyst performance. The presence of aluminates in catalyst compositions has been described in scientific literature such as Catalysts 2015, 5, 145-269. However, the published literature does not describe ways of controlling the formation of aluminates nor does it describe its effect on an OCM catalyst in terms of its selectivity performance.

[0005] Although, supported OCM catalyst systems have been previously described in various publications such as US9963402, none of these publications describe a catalyst system having reduced content of “new phase” oxide species and the improvement in catalyst performance achieved by reducing the formation of such new phase oxide species. The published literature WO20 19048404, describes an OCM catalyst having a silica support and having an active catalyst component comprising manganese and an alkali metal dopant. Although the selectivity performance of the catalyst system disclosed in WO2019048404 is promising, the stability of the catalyst, and product selectivity performance can be further improved for commercial viability. Supported catalyst system represented by the general formula Mn-NazWX SKh has also been described by Arndt et.al in their publication (Applied Catalysis A: General, Volumes 425-426, 28 May 2012, Pages 53-61) and represents a general review article for such OCM catalyst systems. However, as described in the publication, Mn-NazW'CMSiCh catalyst systems are susceptible to deactivation under certain processing conditions, thereby posing additional plant operational challenges.

[0006] Therefore, for the foregoing reasons, there remains a need to develop a supported catalyst systems having reduced new phase oxide species and having one or more benefits of imparting high product selectivity while retaining suitable catalytic stability.

SUMMARY

[0007] A solution to some or all of the drawbacks and limitations described above, resides in the present inventive catalyst composition. Accordingly, the present invention relates to a catalyst composition, comprising:

(a) an oxide phase (A) comprising one or more metal oxide or metal hydroxide components, wherein each of the one or more metal oxide or hydroxide component is represented by a general formula (I): (AE_aRElbRE2_cATd(OH)kO_x) wherein (i) ‘AE’ represents an alkaline earth metal; (ii) ‘RE1 ’ represents a first rare earth element, (iii) ‘RE2’ represents a second rare earth element; (iv) ‘AT’ represents a third rare earth element ‘RE3’, or a redox agent ‘RX’ selected from antimony, tin, nickel, chromium, molybdenum, tungsten, manganese, bismuth; wherein, ‘a’, ‘b’, ‘c’ , and ‘d’ each independently represent relative molar ratio; wherein ‘a’ ranges from about 0 to about 5; ‘b’ ranges from about 0 to about 10; ‘c’ ranges from 0 to about 10; ‘d’ ranges from 0 to about 10; ‘k’ ranges from 0 to about 10; ‘x’ balances the oxidation state and ranges from 0 to 10; wherein, the first rare earth element, the second rare earth element and the third rare earth element are different; and wherein at least one of ‘a’, or ‘b’, or ‘c’ or ‘d’ is greater than zero with the proviso that when ‘k’ is zero then ‘x’ is greater than zero, and when ‘k’ is greater than zero then ‘x’ is zero;

(b) a supported oxide phase (B) comprising one or more metal-support oxide components represented by a general formula (II): (AE_aRElbRE2_cATdM_zO_p) wherein (i) ‘AE’ represents an alkaline earth metal; (ii) ‘RE1 ’ represents a first rare earth element, (iii) ‘RE2’ represents a second rare earth element; (iv) ‘AT’ represents a third rare earth element ‘RE3’, or a redox agent ‘RX’ selected from antimony, tin, nickel, chromium, molybdenum, tungsten, manganese, bismuth; wherein, ‘a’, ‘b’, ‘c’, ‘d’ and ‘z’ each independently represent relative molar ratio; wherein ‘a’ ranges from about 0 to about 5; ‘b’ ranges from about 0 to about 10; ‘c’ ranges from 0 to about 10; ‘d’ ranges from 0 to about 10; ‘z’ ranges from greater than 0 to 10; wherein ‘M’ is a metal selected from aluminum, zinc, tin (II), and lead (II); ‘p’ balances the oxidation state and is greater than zero; wherein, the first rare earth element, the second rare earth element and the third rare earth element are different; and wherein at least one of ‘a’, or ‘b’, or ‘c’ or ‘d’ is greater than zero

(c) a metal oxide support represented by the formula (M_mO_n)t (SiO2)i-t wherein ‘M’ is a metal selected from aluminum, zinc, tin (II), and lead (II); ‘m’, and ‘n’ are any positive number and ranges from about 1 to about 5, ‘t’ ranges from greater 0 to 1; wherein further the weight ratio ‘R’ of supported oxide phase (B) to total weight of oxide phase (A) and supported oxide phase B (i.e B/A+B) is less than equal to (<=) 0.5.

[0008] Further, it is understood by those skilled in art that where reference is made herein to balancing of the oxidation state with respect to the composition, the balancing is to achieve electro- neutrality of the overall composition containing the catalyst of the present invention. In some embodiments of the invention, wherein the weight ratio ‘R’ ranges from 0.08 to 0.45.

[0009] In some embodiments of the invention, the alkaline earth metal ‘AE’ is selected from the group consisting of magnesium, calcium, strontium, barium, and combinations thereof. In some embodiments of the invention, the alkaline earth metal ‘AE’ is strontium. In some embodiments of the invention, the first rare earth element ‘RET, the second rare earth element ‘RE2’, and the third rare element ‘RE3’, are each independently selected from the group consisting of lanthanum, scandium, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, yttrium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and combinations thereof.

[0010] In some embodiments of the invention, the oxide phase (A) comprises one or more metal oxide or metal hydroxide components selected from lanthanum (neodymium) oxide, lanthanum (neodymium) hydroxide, strontium oxide, lanthanum oxide and combinations thereof. In some embodiments of the invention, the supported oxide phase (B) comprises one or more metal oxide components selected from strontium lanthanum (neodymium) aluminum oxide, lanthanum (neodymium) aluminum oxide, lanthanum aluminum oxide, strontium aluminum oxide, strontium (lanthanum) aluminum oxide, and combinations thereof.

[0011] In some embodiments of the invention, the support is an alloy of aluminum oxide and silica having represented by the formula (Ah03)o.94 (Si02)o.o6- In some embodiments of the invention, the support is aluminum oxide represented by the formula (AhChXo (SiC>2)o.o.

[0012] In some aspects of the invention, the invention relates to a method for preparing the catalyst composition of the present invention, wherein the method comprises: a. providing a metal oxide support having the formula (M_mOn)t (SiO2)i-t wherein ‘M’ is a metal selected from aluminum, zinc, tin (II), silicon, and lead (II); ‘m’, and ‘n’ are any positive number and ranges from about 1 to about 5, ‘t’ ranges from greater 0 to 1 ; wherein the metal oxide support is thermally pretreated at any temperature between 1200°C to 2000 °C; b. providing an aqueous solution of a mixed metal oxide precursor comprising at least one compound containing an alkaline earth metal ‘AE’, at least one compound containing a first rare earth element ‘RET, at least one compound containing a second rare earth element ‘RE2’ and at least one compound containing a third rare earth element ‘RE3’ or a redox agent ‘RX’; c. impregnating the metal oxide support (M_mOn)t (SiO2)i-t with the aqueous solution of the mixed metal oxide precursor and forming a supported catalyst precursor; and d. calcining the supported catalyst precursor at a temperature of at least 850 °C and for at least 5 hours, and forming the catalyst composition.

[0013] In some aspects of the invention, the invention relates to a method for preparing the catalyst composition of the present invention, wherein the method comprises: a. impregnating a metal oxide support having the formula (M_mO_n)t (SiC>2 i-t with an aqueous solution comprising one or more compound containing a first rare earth element ‘RET followed by calcination at a temperature of at least 850 °C and for at least 5 hours, wherein ‘M’ is a metal selected from aluminum, zinc, tin (II), silicon, and lead (II); ‘m’, and ‘n’ are any positive number and ranges from about 1 to about 5, ‘t’ ranges from greater 0 to 1; b. providing an aqueous solution of a mixed metal oxide precursor comprising at least one compound containing an alkaline earth metal ‘AE’, at least one compound containing a first rare earth element ‘RET, at least one compound containing a second rare earth element ‘RE2’ and at least one compound containing a third rare earth element ‘RE3’ or a redox agent ‘RX’; c. impregnating the metal oxide support (M_mOn)t (SiO2)i-t obtained from step (a) with the aqueous solution of the mixed metal oxide precursor of step (b) and forming a supported catalyst precursor; d. calcining the supported catalyst precursor at a temperature of at least 850 °C and for at least 5 hours; e. impregnating the supported catalyst precursor obtained from step (d) with an aqueous solution comprising one or more compound containing an alkaline earth metal ‘AE’; and f. calcining the supported catalyst precursor obtained from step (e) at a temperature of at least 850 °C and for at least 5 hours, and forming the catalyst composition.

[0014] In some embodiments of the invention, the one or more compound containing the first rare earth element ‘RET is lanthanum nitrate. In some embodiments of the invention, the one or more compound containing the alkaline earth metal ‘AE’ is strontium nitrate. In some embodiments of the invention, the one or more compound containing the first rare earth element ‘RE1 ’ is lanthanum nitrate and the one or more compound containing the alkaline earth metal ‘ AE’ is strontium nitrate.

[0015] In some aspects of the invention, the invention relates to a process for preparing C2+ hydrocarbon, wherein the process comprises an oxidative coupling of methane using the catalyst composition of the present invention.

[0016] Other objects, features and advantages of the invention will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the invention, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from some specific embodiments may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein.

DETAILED DESCRIPTION

[0017] The invention is based, in part, on the discovery that a supported catalyst system having reduced new phase oxide species would impart one or more benefits of having high product selectivity while retaining suitable catalytic stability. Advantageously, the catalyst composition of the present invention is formulated using suitable modification of the catalyst support, resulting in an improved catalyst performance.

[0018] The following includes definitions of various terms, expressions and phrases used throughout this specification.

[0019] The expressions “about” or “approximately” or “substantially” are defined as being close to as understood by one of ordinary skill in the art. In some non-limiting embodiments the terms are defined to be within 1%, preferably, within 0.1%, more preferably, within 0.01%, and most preferably, within 0.001%.The expressions “wt.%”, “vol.%”, or “mol.%” refers to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume, or the total moles of material that includes the component. In a non-limiting example, 10 moles of a particular component present in a 100 moles of a material is 10 mol.% of component. The use of the words “a” or “an” when used in conjunction with the term “comprising,” “including,” “containing,” or “having” in the claims or the specification may mean “one,” but it is also consistent with the meaning of “one or more,” “at least one,” and “one or more than one.” [0020] The words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”) or “containing” (and any form of containing, such as “contains” and “contain”) are inclusive or open-ended and do not exclude additional, unrecited elements or method steps. The method of the invention can “comprise,” “consist essentially of,” or “consist of’ particular ingredients, components, compositions, etc., disclosed throughout the specification. Any numerical range used through this disclosure shall include all values and ranges there between unless specified otherwise. For example, a boiling point range of 50°C to 100°C includes all temperatures and ranges between 50°C and 100°C including the temperature of 50°C and 100°C.

[0021] The expression “C2+ hydrocarbon” or “C2+ hydrocarbon mixture product” as used in this disclosure means the hydrocarbon products having at least two carbon atoms including ethylene, ethane, ethyne, propene, propane, and C4-C5 hydrocarbons, which are produced using the inventive composition containing the catalyst of the present invention. The expression oxidative coupling of methane or “OCM” as referred or used throughout this disclosure means the oxidative coupling of methane or the reaction of methane and oxygen, for the production of C2+ hydrocarbons from methane. The expression “redox agent” as used though out this disclosure means substances or elements, which are capable of undergoing or promoting either oxidation or reduction reactions. [0022] The expression “selectivity” or “product selectivity” to a desired product or products refers to how much desired product was formed divided by the total products formed, both desired and undesired. For purposes of the disclosure herein, the selectivity to a desired product is a percentage selectivity based on moles converted into the desired product. Further, for purposes of the disclosure herein, a C_x selectivity (e.g., C2 selectivity, C2+ selectivity, etc.) can be calculated by dividing a number of moles of carbon (C) from CH4 that were converted into the desired product (e.g., Cc2H4, Cc2H6, etc.) by the total number of moles of C from CH4 that were converted (e.g., Cc2H4, Cc2H6, Cc2H2,Cc3H6, Cc3H8, Cc4S, Cco2, Cco, etc.). Cc2H4 = number of moles of C from CH4 that were converted into C2H4; Cc2H6 = number of moles of C from CH4 that were converted into C2H6; Cc2H2 = number of moles of C from CH4 that were converted into C2H2; Cc3H6 = number of moles of C from CH4 that were converted into C3H6; Cc3H8 = number of moles of C from CH4 that were converted into C3H8; Cc₄s = number of moles of C from CH4 that were converted into C4 hydrocarbons (C₄s); Cco2 = number of moles of C from CH4 that were converted into CO2; Cco = number of moles of C from CH4 that were converted into CO; etc. Specifically, C2+ hydrocarbon selectivity (e.g., selectivity to C2+ hydrocarbons) refers to how much C2H4, C3H6, C2H2,C2H6, C3H8, Css and C4S were formed divided by the total product formed which includes C2H4, C3H6, C2H2, C2H6, C3H8, C4S, Css, Cn s CO2 and CO. Accordingly, a preferred way of calculating C2+ hydrocarbon selectivity will be by using the equation (Eqn 1):

[0023] Specifically, a high C2+ hydrocarbon selectivity will signify increased formation of useful C2+ hydrocarbon products over that of undesirable carbon oxide byproducts. The term “total product formed” used in the context of measuring selectivity includes C2H4, C3H6, C2H2, C2H6, C₃H₈, C₄s, C₅s, Cn s CO₂ and CO.

[0024] The invention as described in this disclosure provides for a catalyst composition, comprising at least the following components (a) an oxide phase (A) comprising one or more metal oxide or metal hydroxide components, (b) a supported oxide phase (B) comprising one or more metal-support oxide components, (c) a metal oxide support represented by the formula (M_mO_n)t (SiO2)i-t wherein ‘M’ is a metal, and the weight ratio ‘R’ of supported oxide phase (B) to total weight of oxide phase (A) and supported oxide phase B (i.e B/A+B) is less than equal to (<=) 0.5. The inventors surprisingly found that by suitably modifying the metal oxide support, the extent of reaction between the metal oxide support and the oxide/hydroxide species of oxide phase A is limited, resulting in a catalyst having excellent product selectivity performance. A convenient proxy to measure the extent of reaction between the oxide/hydroxide species of phase (A) and the metal-oxide support is by determining weight ratio ‘R’ which if restricted to 0.5 and below, will result in excellent catalyst performance in terms of C2+ hydrocarbon selectivity.

[0025] The expression “oxide phase (A)” as used throughout this disclosure means the portion of the catalyst composition having the one or more oxide and/or hydroxide specie which do not combine chemically with the metal oxide support or in other words are free of metal oxide which is used in support. For the purpose of clarification, if the metal oxide support is alumina, then oxide phase (A) is free of aluminates and does not include alumina. The expression “supported oxide phase (B)” or “new phase” as used throughout this disclosure means the portion of the catalyst composition having the one or more metal-support oxide components, which is a chemical reaction product of the oxide and/or hydroxide specie of the oxide phase A with that of a portion of the metal oxide support (M_mO_n)t (SiC>2 i-t wherein ‘M’ is a metal. For the purpose of clarification, if the metal oxide support is alumina, then the supported oxide phase (B) comprises one or more aluminates formed by the reaction between alkaline metal oxide (AE) or by the oxides or hydroxide species containing rare earth elements ‘RE17’RE2’ or ‘RE3’ with alumina. The expression “new phase content” means the amount of phase B present in the inventive catalyst composition.

[0026] In some embodiments of the invention, the oxide phase (A) comprising one or more metal oxide or metal hydroxide components, wherein each of the one or more metal oxide or hydroxide component is represented by a general formula (I): (AE_aRElbRE2_cATd(OH)kO_x) wherein (i) ‘AE’ represents an alkaline earth metal; (ii) ‘RE1 ’ represents a first rare earth element, (iii) ‘RE2’ represents a second rare earth element; (iv) ‘AT’ represents a third rare earth element ‘RE3’, or a redox agent ‘RX’ selected from antimony, tin, nickel, chromium, molybdenum, tungsten, manganese, bismuth; wherein, ‘a’, ‘b’, ‘c’, and ‘d’ each independently represent relative molar ratio; wherein ‘a’ ranges from about 0 to about 5, 0.1 to about 5, alternatively from about 0.2 to about 1, or alternatively from about 0.1 to about 0.6; ‘b’ ranges from about 0 to about 10, alternatively from about 0.1 to about 10, alternatively from about 0.5 to about 5, alternatively about 0.5 to about 1; ‘c’ ranges from 0 to about 10, alternatively from about 0.1 to about 10, alternatively from about 0.1 to 1, alternatively from about 0.1 to about 0.8; ‘d’ ranges from 0 to about 10, alternatively from about greater than zero to about 1 , alternatively from about greater than zero to about 0.4; ‘k’ ranges from 0 to about 10, alternatively from about greater than zero to about 1, alternatively from about greater than zero to about 0.4; ‘x’ balances the oxidation state and ranges from 0 to 10; wherein, the first rare earth element, the second rare earth element and the third rare earth element are different; and wherein at least one of ‘a’, or ‘b’, or ‘c’ or ‘d’ is greater than zero with the proviso that when ‘k’ is zero then ‘x’ is greater than zero, and when ‘k’ is greater than zero then ‘x’ is zero. [0027] In some embodiments of the invention, the oxide phase (A) comprises one or more metal oxide or metal hydroxide components selected from lanthanum (neodymium) oxide, lanthanum (neodymium) hydroxide, strontium oxide, lanthanum oxide and combinations thereof.

[0028] In some embodiments of the invention, the supported oxide phase (B) comprising one or more metal-support oxide component represented by a general formula (II): (AE_aRElbRE2cATdM_zOp) wherein (i) ‘ AE’ represents an alkaline earth metal; (ii) ‘RE1 ’ represents a first rare earth element, (iii) ‘RE2’ represents a second rare earth element; (iv) ‘AT’ represents a third rare earth element ‘RE3’, or a redox agent ‘RX’ selected from antimony, tin, nickel, chromium, molybdenum, tungsten, manganese, bismuth; wherein, ‘a’, ‘b’, ‘c’ , ‘d’ and ‘z’ each independently represent relative molar ratio; wherein ‘a’ ranges from about 0 to about 5, 0.1 to about 5, alternatively from about 0.2 to about 1, or alternatively from about 0.1 to about 0.6; ‘b’ ranges from about 0 to about 10, alternatively from about 0.1 to about 10, alternatively from about 0.5 to about 5, alternatively about 0.5 to about 1; ‘c’ ranges from 0 to about 10, alternatively from about 0.1 to about 10, alternatively from about 0.1 to 1, alternatively from about 0.1 to about 0.8; ‘d’ ranges from 0 to about 10, alternatively from about greater than zero to about 1, alternatively from about greater than zero to about 0.4; ‘z’ ranges from 0 to about 10, alternatively from about greater than zero to about 1, alternatively from about greater than zero to about 0.4; wherein ‘M’ is a metal selected from aluminum, zinc, tin (II), and lead (II); ‘p’ balances the oxidation state and is greater than zero to 10; wherein, the first rare earth element, the second rare earth element and the third rare earth element are different; and wherein at least one of ‘a’, or ‘b’, or ‘c’ or ‘d’ is greater than zero.

[0029] In some embodiments of the invention, the supported oxide phase (B) comprises one or more metal oxide components selected from strontium lanthanum (neodymium) aluminum oxide, lanthanum (neodymium) aluminum oxide, lanthanum aluminum oxide, strontium aluminum oxide, strontium (lanthanum) aluminum oxide and combinations thereof.

[0030] The expression “different” as used herein means that each of the rare earth elements are different chemical elements. Further, it is understood by those skilled in the art that where reference is made herein to balancing of the oxidation state with respect to the composition, the balancing is to achieve electro-neutrality of the overall composition containing the catalyst of the present invention. [0031] In some embodiments of the invention, the alkaline earth metal ‘AE’ is selected from the group consisting of magnesium, calcium, strontium, barium, and combinations thereof. In some embodiments of the invention, the alkaline earth metal ‘AE’ is strontium. In some embodiments of the invention, the first rare earth element ‘RET, the second rare earth element ‘RE2’, and the third rare element ‘RE3’, are each independently selected from the group consisting of lanthanum, scandium, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, yttrium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and combinations thereof.

[0032] In some embodiments of the invention, the metal oxide support represented by the formula (M_mO_n)t (SiC>2)i-t wherein ‘M’ is a metal selected from aluminum, zinc, tin (II), and lead (II); ‘m’, and ‘n’ are any positive number and ranges from about 1 to about 5, alternatively from about 2 to 4. In some preferred embodiments, the metal ‘M’ is aluminum and ‘m’ being 2 and ‘n’ being 3. In some aspects of the invention, ‘t’ ranges from greater than 0 to 1 , alternatively ‘t’ ranges from 0.9 to 1, or alternatively ‘t’ ranges from 0.92 to 0.98. In some aspects of the invention, ‘t’ indicates whether the metal oxide support is an alloy of metal oxide with silica. In the event when ‘t’ is 1, the metal oxide support comprises only the metal oxide (M_mO_n). In some embodiments of the invention, the support is an alloy of aluminum oxide and silica having represented by the formula (AhC^o .94 (Si02)o .06- In some embodiments of the invention, the support is an aluminum oxide (alumina) represented by the formula (AhChXo (SiC>2)o.o.

[0033] In some embodiments of the invention, wherein the weight ratio ‘R’ ranges from 0.08 to 0.45, alternatively from 0.1 to 0.3, alternatively from 0.15 to 0.25. As demonstrated from the example section (Table 3), when the value of ‘R’ is below 0.5 the selectivity performance of the supported catalyst system is significantly improved.

[0034] The weight ratio may be calculated by first calculating the weight percentage of the various components present in the catalyst composition from the XRD spectral data using the Reference Intensity Ratio (RIR) method. The RIR method involved using the experimental data of peak intensity values which were compared with the data of reference compounds (100% composition, pure) obtained from the database ICDD PDF-2 ver. 2016. As may be appreciated by a skilled person that, since peak intensity and concentration of a component/analyte present in the catalyst composition exhibited a linear relationship, the composition of each phase may be obtained by comparing with the reference data reported in ICDD PDF-2 ver. 2016. [0035] In some embodiments of the invention, the invention is related to a method for preparing the catalyst composition of the present invention, wherein the method comprises: a. providing a metal oxide support having the formula (M_mOn)t (SiO2)i-t wherein ‘M’ is a metal selected from aluminum, zinc, tin (II), silicon, and lead (II); ‘m’, and ‘n’ are any positive number and ranges from about 1 to about 5, ‘t’ ranges from greater 0 to 1; wherein the metal oxide support is thermally pretreated at any temperature between 1200°C to 2000 °C, alternatively at any temperature between 1600°C to 1800 °C b. providing an aqueous solution of a mixed metal oxide precursor comprising at least one compound containing an alkaline earth metal ‘AE’, at least one compound containing a first rare earth element ‘RET, at least one compound containing a second rare earth element ‘RE2’ and at least one compound containing a third rare earth element ‘RE3’ or a redox agent ‘RX’; c. impregnating the metal oxide support (M_mOn)t (SiO2)i-t with the aqueous solution of the mixed metal oxide precursor and forming a supported catalyst precursor; and d. calcining the supported catalyst precursor at a temperature of at least 850 °C, preferably for at least 900 °C and for at least 5 hours, or alternatively for at least 6 hours, and forming the catalyst composition.

[0036] In some aspects of the invention, the metal oxide support having the formula (M_mO_n)t (SiO2)i-t is thermally pretreated prior to impregnation under step (c). Without wishing to be bound by any specific theory, the thermal treatment of the oxide catalyst support at a particular temperature range is particularly useful as it was found that that upon thermally treating the oxide catalyst support within the specific temperature range, the surface area of the oxide catalyst support may be reduced to a level without adversely affecting pore volume of the oxide catalyst support.

[0037] In some aspects of the invention, the invention relates to a method for preparing the catalyst composition of the present invention, wherein the method comprises: a. impregnating a metal oxide support having the formula (M_mO_n)t (SiO2)i-t with an aqueous solution comprising one or more compound containing a first rare earth element ‘RET followed by calcination at a temperature of at least 850 °C, preferably for at least 900 °C and for at least 5 hours, or alternatively for at least 6 hours, wherein ‘M’ is a metal selected from aluminum, zinc, tin (II), silicon, and lead (II); ‘m’, and ‘n’ are any positive number and ranges from about 1 to about 5, ‘t’ ranges from greater 0 to 1 ; b. providing an aqueous solution of a mixed metal oxide precursor comprising at least one compound containing an alkaline earth metal ‘AE’, at least one compound containing a first rare earth element ‘RET, at least one compound containing a second rare earth element ‘RE2’ and at least one compound containing a third rare earth element ‘RE3’ or a redox agent ‘RX’; c. impregnating the metal oxide support (M_mOn)t (SiO2)i-t obtained from step (a) with the aqueous solution of the mixed metal oxide precursor of step (b) and forming a supported catalyst precursor; d. calcining the supported catalyst precursor at a temperature of at least 850 °C, preferably at least 900 °C and for at least 5 hours, or alternatively for at least 6 hours; e. impregnating the supported catalyst precursor obtained from step (d) with an aqueous solution comprising one or more compound containing an alkaline earth metal ‘AE’; and f. calcining the supported catalyst precursor obtained from step (e) at a temperature of at least 850 °C, preferably at least 900 °C and for at least 5 hours, or alternatively for at least 6 hours, and forming the catalyst composition.

[0038] In some embodiments of the invention, the one or more compound containing the first rare earth element ‘RET is lanthanum nitrate. In some embodiments of the invention, the one or more compound containing the alkaline earth metal ‘AE’ is strontium nitrate. In some embodiments of the invention, the one or more compound containing the first rare earth element ‘RE1 ’ is lanthanum nitrate and the one or more compound containing the alkaline earth metal ‘ AE’ is strontium nitrate.

[0039] Without wishing to be bound by any specific theory and by way of this disclosure, it is believed that the synergistic combination of (i) metal oxide catalyst support such as aluminum oxide/alumina, which provides the desired strength to the catalyst with (ii) rare earth elements such as lanthanum, which promotes OCM catalyst activity, (iii) alkaline earth element such as strontium, which promotes C2+ hydrocarbon selectivity, along with (iv) suitable balance of the oxide phase B and oxide phase A, enables the composition containing the catalyst of the present invention, to demonstrate excellent product selectivity. Further, it is believed that the additional treatment of the metal oxide support with a compounds containing rare earth metal ‘RET and alkaline earth metal ‘AE’ mitigates the formation of oxide products of constituting phase B.

[0040] In some embodiments of the invention, the aqueous solution of the mixed metal oxide precursor, comprises at least one compound containing (i) an alkaline earth metal ‘AE’, (ii) at least one compound containing a first rare earth element ‘RET, (iii) at least one compound containing a second rare earth element ‘RE2’ and (iv) at least one compound containing a third rare earth element ‘RE3’. In some embodiments of the invention, the compound containing the alkaline earth metal ‘ AE’, the first rare earth element ‘RET, second rare earth element ‘RE2’ and third rare earth element ‘RE3’ are selected from a nitrate compound, halogen compound, carbonate compound, sulphate compound or a sulphite compound.

[0041] In some embodiments of the invention, the aqueous solution of the mixed metal precursor can be prepared by dissolving in water at least one compound containing an alkaline earth metal ‘AE’, at least one compound containing a first rare earth element ‘RET, at least one compound containing a second rare earth element ‘RE2’, at least one compound containing a third rare earth element ‘RE3’. In some preferred embodiments of the invention, the compound chosen is a nitrate salt for each of alkaline earth metal (AE), the first rare earth element (RE1), the second rare earth element (RE2), and the third rare earth element (RE3). In some embodiments of the invention, the mixed metal oxide precursor is obtained by dissolving the nitrate salts of alkaline earth metal (AE), first rare earth element (RE1), second rare earth element (RE2) in water.

[0042] In some aspects of the invention, a composition comprising a C2+ hydrocarbon mixture product is formed using the composition of the present invention containing the catalyst of the present invention. In some aspects of the invention, C2+ hydrocarbon mixture product comprises ethylene, ethane, ethyne, propene, propane, C4-C5 hydrocarbons, carbon dioxide, carbon monoxide and combinations thereof. In some aspects of the invention, the invention describes a process for preparing a C2+ hydrocarbon mixture product comprising (a) introducing a feed mixture comprising methane and oxygen in a reactor containing the composition comprising the catalyst of the present invention represented by the general formula (I); (b) subjecting the feed mixture to a methane coupling reaction under conditions suitable to produce the C2+ hydrocarbon mixture product; and (c) recovering the C2+ hydrocarbon mixture product after removing unconverted methane from the C2+ hydrocarbon mixture product. In some aspects of the invention, unconverted methane produced during the reaction, is removed from the C2+ hydrocarbon mixture product. In some embodiments of the invention, the removal of unconverted methane from the C2+ hydrocarbon mixture product is effected using a distillation column. In some embodiments of the invention, the distillation column is a cryogenic distillation column.

[0043] Methane coupling reaction under conditions suitable to produce C2+ hydrocarbon mixture product include appropriate temperature conditions, pressure conditions to effect the coupling reaction. In some embodiments of the invention, the feed mixture comprising methane and oxygen may be preheated to a temperature ranging from about 200 °C to about 550 °C, prior to introducing the feed mixture in the reactor for methane coupling. The reactor can comprise an adiabatic reactor, an autothermal reactor, an isothermal reactor, a tubular reactor, a cooled tubular reactor, a continuous flow reactor, a fixed bed reactor, a fluidized bed reactor, a moving bed reactor, and the like, or combinations thereof. In one preferred aspect of the invention, the reactor can comprise an autothermal reactor with short bed. With the small particle size catalyst and short bed design, the pressure drop cross the reactor is within a reasonable range. With the short bed design, good heat back mixing can be achieved, as a result, low temperature feed can be used for reaction. In some preferred aspects of the invention, a 2.3 mm ID quartz tube reactor is used for the purposes of reacting oxygen with methane under conditions sufficient to effect the oxidative coupling of methane. In some aspects of the invention, the reactor comprises an adiabatic reactor. In some aspects of the invention, the C2+ hydrocarbon mixture product is produced at a reactor temperature ranging from about 200°C to about 1000°C, alternatively from about 500 °C to about 950 °C, alternatively from about 700 °C to about 900 °C.

[0044] In some aspects of the invention, the reactor can comprise a catalyst bed comprising the composition capable of catalyzing the oxidative coupling of methane reaction. In some embodiments of the invention, the feed mixture has a methane to oxygen molar ratio ranging from about 2:1 to about 15:1, alternatively from about 4:1 to about 10:1, alternatively from about 5:1 to about 8:1. In some embodiments of the invention, the pressure in the reactor is maintained at a pressure sufficient to effect oxidative coupling of methane. The pressure may be maintained at a range of about 14.7 psi (ambient atmospheric pressure) to about 500 psi, alternatively at a range of about 14.7 psi (ambient atmospheric pressure) to about 200 psi, alternatively at a range of about 14.7 psi (ambient atmospheric pressure) to about 150 psi. In some embodiments of the invention, the feed mixture is introduced into the reactor at a gas hourly space velocity (GHSV) ranging from about 500 h'¹ to about 1,000,000 h’¹, alternatively from about 1,000 h'¹ to about 500,000 h’¹, alternatively from about 5,000 h'¹ to about 400,000 h’¹.

[0045] In some aspects of the invention, the composition containing the catalyst of the present invention, has a C2+ product selectivity hydrocarbon selectivity ranging from about 76.3% to about to about 85%, alternatively from about 76.5% to about 80%, of the total product formed, when the composition is used in a process for producing C2+ hydrocarbon mixture product from methane and oxygen. The expression “total product formed” used in the context of measuring product selectivity includes the products formed of C2H4, C3H6, C2H2, C2H6, C3H8, C4S, C5S, C_{n s}, CO2 and CO. The catalysts obtained above are performance tested in a 2.3 mm ID quartz tube reactor. The catalysts above was sized to 40 to 60 mesh before loading into the reactor. The reactor was loaded with 20 mg of catalyst. A mixture of methane and oxygen at a fixed CH4:O2 ratio of 7.4 was fed to the reactor at a total flow rate of 40.0 seem. Products obtained are analyzed by using online gas chromatograph (GC) with TCD and FID detectors.

[0046] Specific examples demonstrating some of the embodiments of the invention are included below. The examples are for illustrative purposes only and are not intended to limit the invention. It should be understood that the embodiments and the aspects disclosed herein are not mutually exclusive and such aspects and embodiments can be combined in any way. Those of ordinary skill in the art will readily recognize parameters that can be changed or modified to yield essentially the same results.

EXAMPLES

EXAMPLE 1 (Comparative)

[0047] Purpose: The examples as provided here are as a control to evaluate the performance of the inventive catalyst systems. The catalyst system has the formula Sro.sLai.s Ybo.1Ndo.7Ox/Al2O3- (Si02)o.o, where AI2O3 is the metal oxide which functions as a support. Under Example 1, the metal oxide catalyst support was not subjected to thermal pre -treatment nor was the support impregnated with rare earth metal compound and with alkaline earth metal.

[0048] Materials: The following materials are procured and used for the synthesis of the compositions. Table 1 : Inventive catalyst composition (Sro.sLai.s Ybo iNdo ?O_x/A1203-(Si02)o o)

[0049] Catalyst preparation for the purpose of Example 1 : The support was crushed to 20-60 mesh before preparation and was dried at 120 °C overnight prior to use. 2.35 g of strontium nitrate (Sr(NOs)2), 0.50 g of ytterbium nitrate (Yb(NO3)3.6H2O), 8.64 g of lanthanum nitrate (La(NC>3)3.6H2O), and 3.41 g of neodymium nitrate (Nd(NO3)3.6H2O) are dissolved in lOmL of DI water to make a nitrate solution (may be referred to as aqueous solution of a mixed metal oxide precursor) of 0.5 : 0.1 : 1.8 : 0.7 molar ratio of Sr:Yb:La:Nd. After fully dissolving, the nitrate solution (may be referred to as aqueous solution of a mixed metal oxide precursor) is impregnated on the alumina support above until all of the nitrate solution is incorporated into the support. The material obtained was then dried at 120°C and then calcined at 900°C for 6 hours.

[0050] Catalyst evaluation: The catalyst obtained after calcination was evaluated using XRD. The XRD spectral data was used to calculate the ‘R’ value for phase A and Phase B of the catalyst. Further the catalyst performance in terms of their selectivity was evaluated using a 2.3 mm ID quartz tube reactor. For the performance, the catalyst composition obtained was sized to 40 to 60 mesh before loading into the reactor. The reactor was loaded with 20 mg of catalyst. A mixture of methane and oxygen at a fixed CELpCh ratio of 7.4 was fed to the reactor at a total flow rate of 40.0 seem. Products obtained were analyzed by using online GC with TCD and FID detectors. The content of Phase A and Phase B was determined from the XRD spectra using Reference Intensity Ratio (RIR).

[0051] Results: The results from catalyst characterization and performance was evaluated and it is found that in addition to the phases from the active components (Phase A) (SrO, La2(Nd2)C>3, La(Nd)OH3), new phase (Phase B) (LaAlCh, Sr-La-Al-O, Sr-Al-O) that was obtained from the reactions between the active components and AI2O3, as shown in Table 2.

Table 2. Phases in Reference Example 1 catalyst

[0052] From the above data the value of ‘R’ i.e the weight ratio of Phase B/(Phase A and Phase B) was determined as shown below:

R = (8.0+1.0)/(8.0+1.0+7.0+1.0) = 0.52

[0053] The C2+ hydrocarbon selectivity of the catalyst composition prepared under Example 1 is reported at 76.2%. The value of ‘R’ as obtained falls outside the purview of the present invention.

EXAMPLE 2 (Inventive)

[0054] Purpose: For the purpose of Example 2 the metal oxide support was thermally treated at specific predefined temperature prior to impregnation with the active catalyst species.

[0055] Catalyst preparation: Example 2 catalyst was prepared by the same method as Example 1, except that the support was thermally treated at 1500 °C for 3 hours before use. XRD analysis and the catalyst performance testing was carried out as described under Example 1.

[0056] Results: Comparing the results obtained from the inventive Example 2 with that obtained from the practice of Example 1, it was seen that when the support was thermally treated at 1500 °C, the formation of new phase content (phase B) was reduced and accordingly the selectivity of Example 2 was also seen to improve compared to the results obtained from Example 1. The value of ‘R’ is reported to be 0.40 and C2+ hydrocarbon selectivity is reported at 76.8%. EXAMPLE 3 (Inventive)

[0057] Purpose: For the purpose of Example 3 the metal oxide support was thermally treated at a temperature higher than that of Example 2 and subsequently the catalyst performance was evaluated.

[0058] Catalyst preparation: Example 3 catalyst was prepared by the same method as Example 1 , except that the support was thermally treated at 1600 °C for 3 hours prior to catalyst preparation. XRD analysis and the catalyst performance testing was carried out as described under Example 1. [0059] Results: Comparing the results obtained from the inventive Example 3 with that obtained from the practice of Example 2 and Example 1 , it was seen that when the support was thermally treated at 1600 °C, the formation of new phase content (Phase B) was significantly reduced and accordingly the selectivity of Example 3 was higher than what was achieved from both Example 1 and Example 2. The value of ‘R’ is reported to be 0.32 and C2+ hydrocarbon selectivity is reported at 78.4%. From the results obtained from Example 3, it may be concluded that with higher temperature thermal treatment of the catalyst support the C2+ hydrocarbon selectivity performance can be improved by controlling the formation of Phase B.

EXAMPLE 4 (Inventive)

[0060] Purpose: For the purpose of Example 4 the metal oxide support was treated with separate impregnation step involving both rare earth metal ‘RE1 ’ and alkaline earth metal ‘AE’.

[0061] Catalyst preparation: The same support as Example 1 was used for Example 4, but with different preparation protocol as described:

[0062] Impregnation of catalyst support with rare earth metal ‘RE1 ’: 6.24 g of La(NO3)3’6H2O is dissolved in 6mL of distilled water. In 1 mL increments, the dissolved nitrate solution was added dropwise to the above alumina spheres. The alumina mixture was then mixed until homogenously wet, then was placed on a hotplate. The mixture was mixed thoroughly while heated, until the nitrate solution was fully incorporated into the alumina support and the alumina no longer looks damp. Then, another 1 mL of nitrate solution was added dropwise onto alumina, and the process was repeated several times until all of the nitrate solution was incorporated into the support. The material obtained was then dried at 120°C and then calcined at 900°C for 6 hours to obtain calcined La-doped alumina support.

[0063] Impregnation of catalyst support with an aqueous solution of a mixed metal oxide precursor: Next, 2.35 g of Sr(NO3)2, 0.50 g of YbfNCh^’SEbO, 8.64 g of La(NO3)3’6H2O, and 3.41 g of Nd(NO₃)₃«6H₂O were dissolved in lOmL of DI water to make a nitrate solution of 1.0 : 0.1 : 1.8 : 0.7 molar ratio of Sr:Yb:La:Nd (aqueous solution of a mixed metal oxide precursor). After fully dissolving, the nitrate solution was impregnated on the calcined La-doped alumina support with the same method described above until all of the nitrate solution (aqueous solution of a mixed metal oxide precursor) was incorporated into the support. The material obtained was then dried at 120°C and then calcined at 900°C for 6 hours and formed an impregnated support.

[0064] Impregnation of catalyst support with alkaline earth metal ‘AE’: Next, Sr(N()3)2 was dissolved in DI water. The solution obtained was impregnated on the above material with the same method described above until all of the nitrate solution was incorporated into the impregnated support obtained previously. The material obtained was then dried at 120°C and subsequently calcined at 900°C for 6 hours to obtain the metal oxide support.

[0065] The performance testing parameters for determining C₂+ hydrocarbon selectivity and determination of the value of ‘R’ was identical to what was practiced under Example 1.

[0066] Result: The results obtained from the practice of Example 4, indicates a marginal improvement in C₂+ hydrocarbon selectivity. The value of ‘R’ was reported at 0.43 and C₂+ hydrocarbon selectivity at 76.3%.

EXAMPLE 5 (Inventive)

[0067] Purpose: For the purpose of Example 5 the procedure followed was identical to what was practiced under Example 4 except that the metal oxide support was an alloy of alumina and silica with an alumina content of 94 wt.% and represented by the formula (Al₂0₃)o.94-(Si0₂)o.o6 (SA5552 procured from Saint Gobain).

[0068] Catalyst preparation was identical to that of Example 4. The performance testing parameters for determining C₂+ hydrocarbon selectivity performance and determination of the value of ‘R’ was identical to what was practiced under Example 1.

[0069] Result: The results obtained from the practice of Example 5, indicates a significant improvement in C₂+ hydrocarbon selectivity. The value of ‘R’ was reported at 0.11 and C₂+ hydrocarbon selectivity is reported at 79.2%.

[0070] Summary of results from the Examples 1-5: The catalyst performance obtained for Inventive Examples 2-5 is compared with the performance from Example 1. The results are tabulated under Table 3: Table 3: Summary of catalyst performance

[0071] As shown in Table 3, it is evident that by lowering the formation of phase B component, the catalyst composition demonstrated improved performance in terms of C2+ hydrocarbon selectivity. From Example 2 and Example 3, it is evident that by thermal treatment of the catalyst support, the selectivity performance can be improved. From Example 5, it is evident that when the catalyst support comprising the metal oxide (alumina) with a minor amount of silica was specifically treated with a rare earth metal (lanthanum) and an alkali earth metal (strontium), the performance of the catalyst in terms of C2+ hydrocarbon selectivity was significantly improved. Further, for the inventive examples, Examples 2-5, there was no deterioration in catalyst stability observed, thereby indicating their suitability in industrial application in OCM systems.

Claims

1. A catalyst composition, comprising:

(a) an oxide phase (A) comprising one or more metal oxide or metal hydroxide components, wherein each of the one or more metal oxide or hydroxide component is represented by a general formula (I): (AE_aRElbRE2_cATd(OH)kO_x) wherein,

(i) ‘AE’ represents an alkaline earth metal;

(ii) ‘RE1 ’ represents a first rare earth element;

(iii) ‘RE2’ represents a second rare earth element;

(iv) ‘AT’ represents a third rare earth element ‘RE3’, or a redox agent ‘RX’ selected from antimony, tin, nickel, chromium, molybdenum, tungsten, manganese, bismuth; wherein, ‘a’, ‘b’, ‘c’ , and ‘d’ each independently represent relative molar ratio; wherein ‘a’ ranges from about 0 to about 5; ‘b’ ranges from about 0 to about 10; ‘c’ ranges from 0 to about 10; ‘d’ ranges from 0 to about 10; ‘k’ ranges from 0 to about 10; ‘x’ balances the oxidation state and ranges from 0 to 10; wherein, the first rare earth element, the second rare earth element and the third rare earth element are different; and wherein at least one of ‘a’, or ‘b’, or ‘c’ or ‘d’ is greater than zero with the proviso that when ‘k’ is zero then ‘x’ is greater than zero, and when ‘k’ is greater than zero then ‘x’ is zero; and

(b) a supported oxide phase (B) comprising one or more metal-support oxide components represented by a general formula (II): (AEaRElbRE2cATdM_zOp) wherein,

(i) ‘AE’ represents an alkaline earth metal;

(ii) ‘RE1 ’ represents a first rare earth element;

(iii)‘RE2’ represents a second rare earth element; and

(iv)‘AT’ represents a third rare earth element ‘RE3’, or a redox agent ‘RX’ selected from antimony, tin, nickel, chromium, molybdenum, tungsten, manganese, bismuth; wherein, ‘a’, ‘b’, ‘c’, ‘d’ and ‘z’ each independently represent relative molar ratio; wherein ‘a’ ranges from about 0 to about 5; ‘b’ ranges from about 0 to about 10; ‘c’ ranges from 0 to about 10; ‘d’ ranges from 0 to about 10; ‘z’ ranges from greater than 0 to 10; wherein ‘M’ is a metal selected from aluminum, zinc, tin (II), and lead (II); ‘p’ balances the oxidation state and is greater than zero; wherein, the

22 first rare earth element, the second rare earth element and the third rare earth element are different; and wherein at least one of ‘a’, or ‘b’, or ‘c’ or ‘d’ is greater than zero; and

(c) a metal oxide support represented by the formula (M_mO_n)t (SiC>2 i-t wherein ‘M’ is a metal selected from aluminum, zinc, tin (II), and lead (II); ‘m’, and ‘n’ are any positive number and ranges from about 1 to about 5, ‘t’ ranges from greater 0 to 1; wherein further the weight ratio ‘R’ of supported oxide phase (B) to total weight of oxide phase (A) and supported oxide phase B (i.e B/A+B) is less than equal to (<=) 0.5.

2. The catalyst composition of claim 1 , wherein the weight ratio ‘R’ ranges from 0.08 to 0.45.

3. The catalyst composition of claim 1 , wherein the alkaline earth metal ‘ AE’ is selected from the group consisting of magnesium, calcium, strontium, barium, and combinations thereof.

4. The catalyst composition of claim 1, wherein the alkaline earth metal ‘AE’ is strontium.

5. The catalyst composition of claim 1, wherein the first rare earth element ‘RET, the second rare earth element ‘RE2’, and the third rare element ‘RE3’, are each independently selected from the group consisting of lanthanum, scandium, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, yttrium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, and combinations thereof.

6. The catalyst composition of claim 1, wherein the oxide phase (A) comprises one or more metal oxide or metal hydroxide components selected from lanthanum (neodymium) oxide, lanthanum (neodymium) hydroxide, strontium oxide, lanthanum oxide and combinations thereof.

7. The catalyst composition of claim 1 , wherein the supported oxide phase (B) comprises one or more metal oxide components selected from strontium lanthanum (neodymium) aluminum oxide, lanthanum (neodymium) aluminum oxide, lanthanum aluminum oxide, strontium aluminum oxide, strontium (lanthanum) aluminum oxide and combinations thereof.

8. The catalyst composition of claim 1, wherein the support is an alloy of aluminum oxide and silica having represented by the formula (AhC^o .94 (Si02)o 06-

9. The catalyst composition of claim 1, wherein the support is aluminum oxide represented by the formula (AhCh .o (Si02)o.oo.

10. A method for preparing the catalyst composition according to claim 1 , wherein the method comprises: a. providing a metal oxide support having the formula (M_mOn)t (SiO2)i-t wherein ‘M’ is a metal selected from aluminum, zinc, tin (II), silicon, and lead (II); ‘m’, and ‘n’ are any positive number and ranges from about 1 to about 5, ‘t’ ranges from greater 0 to 1 ; wherein the metal oxide support is thermally pretreated at any temperature between 1200°C to 2000 °C; b. providing an aqueous solution of a mixed metal oxide precursor comprising at least one compound containing an alkaline earth metal ‘AE’, at least one compound containing a first rare earth element ‘RET, at least one compound containing a second rare earth element ‘RE2’ and at least one compound containing a third rare earth element ‘RE3’ or a redox agent ‘RX’; c. impregnating the metal oxide support (M_mOn)t (SiO2)i-t with the aqueous solution of the mixed metal oxide precursor and forming a supported catalyst precursor; and d. calcining the supported catalyst precursor at a temperature of at least 850 °C and for at least 5 hours, and forming the catalyst composition.

11. A method for preparing the catalyst composition according to claim 1 , wherein the method comprises: a. impregnating a metal oxide support having the formula (M_mO_n)t (SiC>2 i-t with an aqueous solution comprising one or more compound containing a first rare earth element ‘RET followed by calcination at a temperature of at least 850 °C and for at least 5 hours, wherein ‘M’ is a metal selected from aluminum, zinc, tin (II), silicon, and lead (II); ‘m’, and ‘n’ are any positive number and ranges from about 1 to about 5, ‘t’ ranges from greater 0 to 1; b. providing an aqueous solution of a mixed metal oxide precursor comprising at least one compound containing an alkaline earth metal ‘AE’, at least one compound containing a first rare earth element ‘RET, at least one compound containing a second rare earth element ‘RE2’ and at least one compound containing a third rare earth element ‘RE3’ or a redox agent ‘RX’; c. impregnating the metal oxide support (M_mOn)t (SiO2)i-t obtained from step (a) with the aqueous solution of the mixed metal oxide precursor of step (b) and forming a supported catalyst precursor; d. calcining the supported catalyst precursor at a temperature of at least 850 °C and for at least 5 hours; e. impregnating the supported catalyst precursor obtained from step (d) with an aqueous solution comprising one or more compound containing an alkaline earth metal ‘AE’; and f. calcining the supported catalyst precursor obtained from step (e) at a temperature of at least 850 °C and for at least 5 hours, and forming the catalyst composition.

12. The method of claim 11, wherein the one or more compound containing the first rare earth element ‘RET is lanthanum nitrate.

13. The method of claim 11, wherein the one or more compound containing the alkaline earth metal ‘AE’ is strontium nitrate.

14. A process for preparing C2+ hydrocarbon, wherein the process comprises an oxidative coupling of methane using the catalyst composition of claim 1.

25